Conventionally, radar image display devices which create and display a radar image based on one or more echo signals received from a radar antenna has been known. In some of the radar image display devices, menu indications have been devised to display the radar image enlarged on a display screen. JP10-239419A discloses this kind of radar image display device, for example.
The radar image display device disclosed in JP10-239419A classifies various menu items into menu items for steady (i.e., static) information indications and menu items for non-steady (i.e., dynamic) information indications. The steady information includes information which must be displayed, for example by international standards, and information which a user always wants to observe (information on a ship position, a ship speed, a heading, etc.), and it is always displayed on a corner part of a display screen. Whereas, the non-steady information is displayed overlapping with a radar image when a predetermined operation is performed by a user. Thus, a radar image can be displayed enlarged, while maintaining operability to some extent.
As for other methods of displaying a radar image, JP05-002065A discloses a configuration where an azimuth scale is additionally displayed on a range ring (distance ring), and JP08-105954A discloses a configuration where ranges which are usually used can be selected by a user by displaying a list of available ranges (display distance range).
In recent years, an information display device has been proposed. This device receives data including positional information of a ship and school-of-fish information as well as echo signals, and executes an application according to the received data to display, for example, a radar image, an electronic nautical chart around the ship, and an image of the school-of-fish information. This kind of information display device can switch an image displayed on a display screen from one to another based on an instruction from the user.
However, since types and number of menu items required for each image displayed are different, the conventional information display devices described above typically display the menu items differently at different positions in the display screen for different images. Therefore, a user must study the display positions and the selection manners for every application, confusing the user when selecting a menu item.